Progress in treating pulmonary and other complications of striated muscle deterioration in Duchenne muscular dystrophy (DMD) patients has made cardiomyopathy a leading cause of mortality. Limited ambulation due to skeletal muscle weakness in DMD often masks typical symptoms seen in other populations with myocardial disease, allowing unchecked disease progression. Without aggressive screening, DMD patients' first manifestation of heart disease may be severe heart failure or sudden cardiac death. Our group and others have detected myocardial fibrosis in DMD patients prior to reduction in left ventricular ejection fraction (EF) using cardiac magnetic resonance (CMR). Also, with CMR-derived strain measurement, a more sensitive marker of contractile dysfunction, we have found subclinical decline that occurs annually. Recognizing fibrosis with preserved EF led to the idea that old cardiac drugs with reported 'antifibrotic' effect might be beneficial in DD cardiomyopathy. An engaged family launched a fundraising effort that fueled rapid testing of our hypothesis. We subsequently published in less than 12 months from start date remarkable preclinical data showing that early treatment of a DMD mouse model with aldosterone inhibition plus an angiotensin converting enzyme inhibitor (ACEI) affords dramatic reduction in muscle injury and preserved muscle function in both heart and skeletal muscles. Current guidelines advocate initiation of e.g. an angiotensin converting enzyme inhibitor (ACEI) when the EF falls below normal, but our data suggest that earlier treatment should be considerably more beneficial. We have made significant progress since publication of this work in August 2011 that will allow us to rapidly execute 3 essential next steps: i) a preclinical study designed to identif the optimal aldosterone antagonist for the dystrophic heart; ii) a cardiac clinical trial with structural, functional and serological endpoints; and iii) a mechanistic study focused on defining pathways of efficacy in order to optimize future treatment of all affected muscles in DMD. To address these critical issues, we have assembled a strong interdisciplinary team to execute both a landmark patient study of aldosterone antagonism plus ACEI in preserved EF DMD boys and parallel mouse experiments to precisely define which nuclear receptors in different striated muscle types mediate the observed therapeutic effects. In proving our hypotheses regarding efficacy in attenuating preclinical changes, the clinical studies will use state-of-the-art noninvasive CMR biomarkers of subclinical contractile dysfunction and fibrosis. This data will provide much-needed evidence for patients, families and providers dealing with this devastating disease that existing drugs - already in use for other indications in children and adults - offer a potential cardioprotective benefit. Successful execution of the preclinical studies will provide th necessary insights for rational design of therapeutics to have the greatest impact on reducing death and disability in patients with DMD.